In computing and in embedded systems, a programmable interval timer (PIT) is a counter that generates an output signal when it reaches a programmed count.
Periodic timers are typically used to invoke activities that must be performed at regular intervals.
The Intel 8253 PIT was the original timing device used on IBM PC compatibles.
[2] The LAPIC in newer Intel systems offers a higher-resolution (one microsecond) timer.
[3] This is used in preference to the PIT timer in Linux kernels starting with 2.6.18.